4. The average age of readmissions was 80.3 years for patients originally hospitalized for heart failure, 79.8 years for patients originally hospitalized for acute myocardial infarction and 80 years for patients originally hospitalized for pneumonia.

Timing and frequency5. The majority of all readmissions occurred within 15 days of hospitalization: Sixty-one percent of heart failure readmissions, 67.6 percent of acute myocardial infarction readmissions and 62.6 percent of pneumonia readmissions occurred in this time period.

6. Among all readmissions, approximately one-third occurred from day 16 through day 30 post-hospitalization.

7. The median time period between hospitalization and readmission was 12 days for heart failure patients, 10 days for acute myocardial infarction patients and 12 days for pneumonia patients.

8. Of readmissions after a heart failure hospitalization, 87.5 percent were readmitted once, 9.7 percent were readmitted twice and 2.8 percent were readmitted three or more times.

9. Of readmissions after an acute myocardial infarction hospitalization, 97.4 percent were readmitted once, 2.4 percent were readmitted twice and 0.2 percent were readmitted three or more times.

10. Of readmissions after a pneumonia hospitalization, 95.1 percent were readmitted once, 4.3 percent were readmitted twice and 0.6 percent were readmitted three or more times.

Readmission diagnoses11. Of readmissions after a heart failure hospitalization, the most common diagnosis was heart failure at 35.2 percent.

12. Of readmissions after an acute myocardial infarction hospitalization, the most common diagnosis was heart failure at 19.3 percent.

13. Of readmissions after a pneumonia hospitalization, the most common diagnosis was recurrent pneumonia 22.4 percent.

14. Cardiovascular disease was the cause of 52.8 percent of readmissions after heart failure hospitalization and 53.4 percent of readmissions after acute myocardial infarction hospitalization.

16. The five most common readmission diagnoses accounted for 55.9 percent for heart failure readmissions, 44.3 percent of acute myocardial infarction readmissions and 49.6 percent of pneumonia readmissions.

In the study titled "Pediatric Readmission Prevalence and Variability Across Hospitals," researchers studied 568,845 admissions at 72 children's hospitals between July 1, 2009 and June 30, 2010. The authors categorized hospitals as having high readmission rates if the rates were one standard deviation above the mean, and low readmission rates if they were one standard deviation below the mean. The researchers found the following:

17. The 30-day unadjusted readmission rate for all hospitalized children was 6.5 percent.

18. The adjusted 30-day readmission rate for hospitals with high readmission rates were 7.2 percent compared with 5.6 percent for low-readmission hospitals — a difference of 28.6 percent.

19. Adjusted 30-day readmission rates for the 10 admission diagnoses with the highest readmission prevalence were 17 percent to 66 percent greater in hospitals with high readmission rates compared with hospitals with low readmission rates.

20. The 30-day readmission rate for sickle cell, one of the 10 diagnoses with the highest rate of readmissions, were 20.1 percent in hospitals with high readmission rates and 12.7 percent in hospitals with low readmission rates.